Yes, it is operated by a stepper motor instead of mechanical linkage. A centrifugal governor gear is mentioned in the parts list, but apparently it is not used in this particular generator. They may use this engine on another generator that does have the mechanically controlled governor linkage.
View attachment 13905
On the schematic, this is the stepper motor that controls the throttle....
View attachment 13906
So, the stepper motor is operated by a control board assembly (the 549407 part shown) which would be sensing the generator output frequency and adjusting the stepper motor as needed. In my opinion, they have the frequency set too high. But, if they are not willing to send another controller, and you choose not to return the generator, then you are stuck with it being a little high as it can't be adjusted like a mechanical governor.
Just to be sure that your meter is calibrated, check the line frequency at a wall plug and see if the meter reads 60Hz.